WO2010081491A1

WO2010081491A1 - Small direct-injecting diesel engine

Info

Publication number: WO2010081491A1
Application number: PCT/EP2009/000286
Authority: WO
Inventors: Matthias Lamping
Original assignee: Fev Motorentechnik Gmbh
Priority date: 2009-01-18
Filing date: 2009-01-18
Publication date: 2010-07-22
Also published as: DE112009003869A5

Abstract

The present invention relates to a diesel combustion engine, which comprises at least one or more cylinders (2), each having a displacement of approximately 250 ccm at the most, preferably less than 250 ccm, wherein a cylinder (2) comprises a delimitation of a combustion chamber (3) in a conical shape by a cylinder head (4) of the diesel combustion engine (1), an injection system (11) which is arranged at least approximately centrally and centrically in the conical shape, a piston (5) having a piston bowl (8), and an intake valve and channel system and geometry for generating a swirl in the combustion chamber (3) of the cylinder (2), and is provided with individual intake and outlet valves (13, 14), wherein the intake and outlet valves (13, 14) are arranged opposite of each other in the cylinder head (4). Furthermore, a diesel-engine combustion method for a small displacement is proposed.

Description

Small direct-injection diesel engine

The present invention relates to a diesel internal combustion engine having a cylinder capacity of approximately at most 250 cm ³ and a corresponding method for diesel engine combustion in an internal combustion engine having at least one cylinder with a capacity of at most 250 cm ³ .

Even stricter requirements on the exhaust behavior of internal combustion engines, especially in vehicles as well as higher costs in relation to the operation of motor vehicles lead to explore a variety of different ways, such as reducing the cost of operating an internal combustion engine and on the other hand, the ever stricter conditions fair operation an internal combustion engine can be enabled.

The object of the present invention is to provide an internal combustion engine which, on the one hand, satisfies the particularly increased CO ₂ emission limit values according to the current and future EU directive, on the other hand offers a potential for saving fuel, such an internal combustion engine still being usable, preferably in US Pat vehicles.

This object is achieved with a diesel internal combustion engine with the features of claim 1 and with a method for diesel engine combustion with the features of claim 15. Advantageous applications are given in the further claims. The following features illustrated by way of individual embodiments are not limited to this particular embodiment. Rather, one or more features of one or more embodiments may also be linked together to form further developments.

A diesel internal combustion engine is proposed, which has at least one or more cylinders, each having a displacement of approximately at most 250 cm ³ , preferably less than 250 cm ³ , wherein a cylinder is a boundary of a combustion chamber in a cone shape through a cylinder head of the diesel Internal combustion engine having an injection at least approximately centrally and centrally located in the cone shape having a piston with a piston recess, an intake valve and duct arrangement and geometry for generating a swirl in a combustion chamber of the cylinder, and is provided with a respective single intake and exhaust valve, wherein the inlet and the exhaust valve are arranged opposite to each other in the cylinder head.

The proposed approach for a diesel internal combustion engine pursues the principle of downsizing consistently for the diesel combustion process, the proposed form of displacement, by a homogenization of the fuel-air mixture extremely efficient energy conversion on the one hand and on the other hand low CO ₂ emissions. For example, a proposed diesel internal combustion engine can be used as a single cylinder. It is also possible to produce an approximately one liter displacement engine, which is equipped as a diesel internal combustion engine according to the proposal with four or more cylinders, each up to 250 cm ³ . For example, in this way a six-cylinder engine with such a diesel internal combustion engine can be formed, which has a total displacement of about 1.5 liters. A further embodiment provides, for example, the use of two or three cylinders with respective displacements of approximately at most 250 cm ³ . An application of the proposed diesel internal combustion engine may relate to the field of two-wheeled vehicles. For example, a proposed diesel internal combustion engine can be used in a motorcycle. Another embodiment provides that the diesel internal combustion engine is used as a so-called range extender. In this case, such a diesel internal combustion engine supports a hybrid vehicle or even a pure electric vehicle. The diesel internal combustion engine is used when an increased mileage is required, on the other hand, a battery state of charge can not cover this. The range extender is then able to provide the necessary energy for further operation of the vehicle, in particular motor vehicle. The energy can either be supplied directly to the accumulator or else the diesel internal combustion engine is able to transmit a torque to the drive shaft of the motor vehicle. Other applications of the proposed diesel internal combustion engine may be in the area of small vehicles, such as lawnmowers, gritting vehicles, skijets or even waterjets, small waterborne vehicles as well as airborne vehicles. The proposed diesel internal combustion engine has a structure in which preferably the conical shape in the cylinder head is continuous. It is particularly advantageous if the conical shape in the cylinder head is designed to be completely rotationally symmetrical as the boundary of the combustion chamber. The cone shape can be interrupted, for example, by the injection as well as by the inlet and outlet valves. In this case, it is preferred that the inlet valve as well as the outlet valve terminate as flush as possible in the closed state with the conical shape. According to one embodiment, it can be provided here that a valve disk has a curvature corresponding to the conical shape, so that when the valve is closed a smooth transition takes place from the cylinder head via the valve seat edge to the valve outer surface, which is rounded in accordance with the conical shape. For this purpose, the valve is held so that rotation about a valve longitudinal axis remains suppressed. According to another embodiment, the valve is held so that it can rotate about its valve longitudinal axis. In such an embodiment, the valve has, for example, a surface facing the combustion chamber, which is a plane. Another embodiment of a valve has a curved surface, which can extend inwardly towards the combustion chamber as well as outwardly away from the combustion chamber. The conical shape can furthermore be described in cross-section essentially by two converging straight lines. However, the conical shape can also be formed by two or more degree sections which, when lined up, each produce a lateral cross section in the form of cones and run towards one another. Furthermore, a rounded, in particular calotte-like, also spherical-caliber-like design can result in the conical shape as a boundary of the combustion chamber. It is preferred that the limitation in the cylinder head is as rotationally symmetrical as possible.

The injection is preferably arranged at least approximately centrally and centrally in the conical shape of the cylinder head. An axis of an injection nozzle of the injection is also preferably parallel to a cylinder axis, in particular can coincide with this. There is also the possibility that an injection axis is inclined to the cylinder axis. However, it is preferred that such an inclination is less than 20 degrees, preferably less than 10 degrees. A further development of the injection provides that a nozzle with several holes is used. In this case, a nozzle injection jet preferably results in a conical shape starting from an injection axis. The conical shape of the injection may, according to one embodiment, approximately coincide with a conical shape of the boundary in the cylinder head. Preferably, an injection is adapted to the piston recess in the piston itself. If, for example, a conical injection is produced by arranging a nozzle opening or through several nozzle holes of the injection, it is provided according to one embodiment that the Piston well is positioned during operation of the diesel internal combustion engine in at least one operating range so that they can receive the respective injection jet on their soil. According to a further embodiment, it is provided that the piston forms a rotationally symmetrical limitation of the displacement with the piston recess. Preferably, the piston recess is a round, in particular annular, channel shape on the piston surface. For example, the piston recess may be axisymmetric, wherein preferably the axis of symmetry coincides with the cylinder axis.

According to one embodiment, it is provided that, starting from an outer edge of the piston, the piston recess drops radially inwards and rises again toward the center of the piston. Viewed in cross section, in particular a geometry of the trough can be selected, which in this case has a radius. Such a radius may for example be between 35 mm and 50 mm, preferably between 38 and 43 mm. The cross section of the trough may in particular also have a hyperbolic course. The piston recess may according to a further embodiment have different slopes along its course in the piston. Thus, the opposing walls of the piston bowl, starting from a piston bowl bottom differently shaped as well as having a different pitch from each other. Also, a dimple in the piston can lead to the formation of an overhang in one side. A piston bowl bottom may be rounded according to one embodiment. Another embodiment provides that the piston recess bottom is at least partially flat, preferably forms a circumferential plane around the cylinder axis. The piston bowl may be symmetrical when viewed along a cutting plane that extends along the cylinder axis. However, the piston recess can also be displaced along this cutting plane closer to an edge of the piston or else to a center of the piston, symmetrically or asymmetrically. A further embodiment provides, for example, that the piston recess in the region of the piston center has a rise, which rises in particular over the piston edge in the direction of the cylinder head. In this way, for example, this elevation separates the round, circumferential channel, which thus forms a one-piece piston recess, but forms along a cross-section through the piston with a cross-sectional plane along the cylinder axis thus a two-fold depression geometry along the diameter. The elevation is then arranged between the two well geometries and may preferably be flattened or rounded in an upper area. Preferably, the slope of the hill is adapted to the boundary of the combustion chamber in the cylinder head, preferably therefore conical at least at intervals. The hill can be pointed or rounded in an upper area. A further embodiment provides that the hill has a flattening, for example in the form of a plateau. Another embodiment of the piston recess provides that it falls off from the outer edge of the piston ago, preferably at least at an angle of more than 70 °, relative to a horizontal. The angle can also be at least approximately 90 °. According to a further embodiment, this can also change when falling to the trough bottom. For example, the lateral trough drop may also have an angular range which is greater than 90 ° and forms a recess in the steeply sloping trough wall. Preferably, the trough bottom then rises again at an angle to the center of the piston, which is much flatter than the falling angle near the piston edge. Here, the trough is preferably over into a hill which, for example, extends at least approximately at the level of the piston edge, preferably above the piston edge. In this way, in particular a depression geometry can be created, which is preferably at least approximately rotationally symmetrical. A lowest point of the piston crown, for example, is arranged closer to the edge of the piston than to the center of the piston. Preferably, the lowest point is arranged in a region which is up to about 1/3 radius distance from the piston edge, preferably in a range which is up to about% radius distance from the piston edge. According to a further development, the piston crown then rises, in which case it is preferably rounded, more preferably in this case makes a change in pitch, in particular has a turning point in the slope, so that the center of the piston, the piston head continues to increase, but the slope is lower. A maximum height, the piston crown preferably at the Annhöhe, but it may also have on the piston edge. Preferably, the rising piston crown has a virtual intersection with a horizontal and thus perpendicular to the cylinder axis, which runs along the piston edge, wherein the intersection is preferably arranged in a region which is less than the 4/7 radius viewed from the piston center is preferably less than ^Λ Λ radius from the center of the piston, preferably in a range between 4/7 radius and% radius of the piston center, more preferably in a range! 4 radius to% radius of the piston center. It is further preferred that the piston recess extends at least around the piston axis through 360 °. Preferably, the piston recess is continuous, preferably even rotationally symmetrical.

Moreover, according to one embodiment, the piston recess can also have a continuous, axially symmetrical shape, preferably oval. Moreover, it can only be round in sections and have short sections which are almost straight. There is also the possibility that a greatest depth of the piston recess, based on a cross section through the piston recess, changes. So the piston ground also change along its rotating extent, for example, rise and fall again. Also, a geometry of the cylinder head opposite the piston and preferably the piston recess can be adapted to the course of the piston recess. For example, a combustion chamber wall in the cylinder head can not only be round but also oval in cross section.

A fuel jet is in a trough mold having a center of gravity in the direction of the piston edge, for example, injected such that it is deflected from the trough bottom, preferably from the trough edge back up and preferably with a direction in the center of the combustion chamber. If the fuel is already at least partially evaporated, a corresponding vaporized fuel flow is deflected accordingly. For example, a trough bottom or trough wall arranged on the piston edge can have an indentation for this purpose, which causes a deflection of a fuel flow that has entered the trough upwards in the direction of the center of the piston.

Preferably, a swirl is generated which has a rotational component which extends around the cylinder longitudinal axis. An embodiment provides that the rotational component about the cylinder longitudinal axis is induced as the main flow in the combustion chamber. In particular, a vortex can be generated in the form of a swirl. However, there is also the possibility that the swirl produced has a portion which has a different direction of rotation. Thus, for example, the direction of rotation can be adapted to an orientation of the injection, in particular an inclination of the injection and / or a shape and orientation of the trough in the piston.

Furthermore, it is provided that for generating a twist, in particular a

Swirls preferred an eccentric seat of the inlet valve is provided. As a result, a seat swirl phase can be formed, so that even a swirl-induced flow can be generated during a small valve lift. A support of a twist, in particular a swirl and in particular a degree of filling is preferably achieved in that an inlet channel arrangement is present as possible without curvature, in particular without execution as a spiral channel. A geometry of the channel provides in this case that as far as possible no disturbances and in particular angular courses are provided which produce a twist other than the desired swirl flow, in particular swirl flow. Therefore, an approximately rectilinear supply of the inlet channel to the inlet valve in the cylinder head is preferred. Support for a swirl formation can furthermore be achieved, for example, by providing flow devices, for example a preferably adjustable flow baffle. Also, the inlet channel may be divided, for example. Furthermore, it is provided that the respective individual inlet and outlet valve can preferably be driven by means of a single camshaft in accordance with one embodiment. Another embodiment provides that two camshafts are used, wherein the one camshaft drives the respective intake valve of one or more cylinders and the other camshaft drives the respective exhaust valve of the cylinder or cylinders. Other drives for one or more valves can also be used. For example, a valve lift can be provided. For this purpose, the camshaft either itself have a corresponding device for Hubveränderung. There is also the possibility that a camshaft bearing allows such a change in the valve lift, for example by an eccentric adjustment of the position. In addition, it can also be provided that the valve itself is able to enable different valve strokes by changing the valve length can. In addition, it is possible to use electromagnetic or other drives that can allow free control of the valve lift regardless of the mandatory specification of a revolution of a crankshaft. In this case, for example, consideration is given to the fact that clearance must be provided due to the inclination of the valves. By means of a variable valve drive, a change of the valve lift over the rotational speed range of the diesel internal combustion engine is provided in particular. Thus, for example, depending on the load, a different valve lift can be provided at the inlet as well as, for example, additionally or alternatively at the outlet valve. It is also possible, by means of a variable valve train, to be able to adapt the valve timing to a change in the direction of injection early or late. This can take place by means of a corresponding engine control or valve control. It is also possible, by means of a variable valve train control, to overlap opening times of intake and exhaust valves so that, for example, an internal exhaust gas recirculation is made possible.

According to one embodiment, for example, it is provided that the diesel internal combustion engine is air-cooled. For this purpose, for example, in addition an oil supply for lubrication miteingesetzt, which absorbs heat and dissipates and then can deliver via a suitable cooler. Further cooling of the cylinder head or the engine block, in which the one or more cylinders are arranged, otherwise takes place, for example, via corresponding cooling air supply lines. Another embodiment provides that one or more coolant flows are passed through the diesel internal combustion engine. These can be coupled with an oil circuit and also cool it. It is preferably provided here that an or a plurality of heat exchangers are provided which allow, for example by means of additional air supply by one or more fans, a removal of the necessary heat. A cooling circuit of the diesel internal combustion engine can also be designed to be split. In this case, for example, a first part of a coolant flows exclusively around the cylinder head, while a second part, for example, flows exclusively around the engine block. Both cooling streams can then be reconnected and cooled together. It is also possible to provide shared cooling circuits as well as switches that are controlled, for example thermally or by driving pulses, by means of which a cooling circuit can be activated or interrupted, in particular sub-circuits can be activated or interrupted.

The diesel internal combustion engine may include additional passive cooling devices, such as cooling fins, particularly near the cylinder head as well as near each cylinder. As a material for the diesel internal combustion engine, for example, a light metal alloy, preferably an AlMg alloy, vermicularguss, cast iron, in particular ductile iron as well as for various components such as cylinder head, crankcase, oil pan and any attachments different materials can be used.

The diesel internal combustion engine further preferably has a common rail device, via which a plurality of cylinders can be connected to one another and supplied with diesel fuel, or else only a single cylinder can be operated. The common rail injection is preferably in two stages. However, it can also be carried out in another way. In addition, there is the possibility that each cylinder a single injection pump is provided. In particular, when using only one or two or three cylinders, an injection pump can be provided directly on the cylinder head for each cylinder.

A further embodiment provides for a diesel internal combustion engine in which the injection jets of the injection form a cone angle which lies between 70 ° and 90 ° relative to an axis through an injection nozzle of the injection. Preferably, such a tapered-angle injection is coupled to a well geometry such that the injection jets impinge on a bottom of the piston bowl as the piston moves in the cylinder. In this case, it is preferred that the injection jets strike approximately centrally on the respective bottom of the piston recess, in particular when the piston is at least approximately in the TDC position. Preferably, the conical shape of the injection jets combined with a piston recess as described above, in the one Trough channel preferably concentric around the center of the piston extends 360 °. In this way, a uniform distribution of the injected fuel can take place and use by forming a swirl a homogenization of the fuel-air mixture. It is preferred if such a cone angle of the injection radiation is in a range between 78 ° and 83 °, preferably around 80 °. Here it is assumed that the injection nozzle is parallel to the cylinder axis and in particular coincides with this. If the injection nozzle is arranged slightly angled in the cylinder head, this may result in a certain change in the described conical region for the injection jets. This shift results from the idea of being able to achieve the most uniform possible distribution of the fuel in the cylinder using the local flow conditions.

Furthermore, it is preferred if the inlet and the outlet valve each have an angle of inclination between a valve axis and a cylinder axis, which are each in a range between 20 ° and 30 °. Preferably, the inclination angle has a range between 23 ° and 26 °, in particular, the inclination angle is about 24.5 °. With such an arrangement, a still rigid cylinder head construction can be made possible on the one hand. For example, a combustion chamber internal pressure of 200 bar and more is possible during the combustion process, which can be absorbed by appropriate stiffening of the cylinder head. The arrangement of the valve axes allows such a rigid construction and securing of the conical boundary of the combustion chamber is made possible. It is preferred here that an injector thickness of an injection of less than 2 cm is present, in particular preferably of approximately 14 mm. Furthermore, it is preferred if in the cylinder head for the inlet and the outlet valve in each case a valve seat diameter is provided which is between 20 mm, in particular 31 mm to 37 mm, wherein preferably a range between 33 and 36 mm, particularly preferably 34 mm. The diameter is different for particular different displacement as well as bore diameter of the cylinder. For example, with a cubic capacity of 200 cc and a bore diameter of 63 mm, a valve seat diameter is preferably 31 mm to 37 mm. A further embodiment provides, for example, that the inlet and the outlet valve have the same angle of inclination. A further embodiment also provides that, for example, the valve seat diameter of the inlet and the outlet valve is at least approximately equal. The arrangement of the valves as well as the channel guide allows a rotationally symmetrical design of the combustion chamber, whereby a particularly preferred even homogenization can take place when forming a matched swirl flow in the combustion chamber. A further embodiment provides that the individual inlet channel in the cylinder head is designed as a filling channel. Here, the inlet channel is formed with the lowest possible flow resistance. The inlet channel in this case preferably has a diameter between 25 mm and 31 mm, particularly preferably with a displacement of about 0.2 liters. Is the displacement larger or smaller, so that the diameter can be larger or smaller.

According to a further aspect of the invention, a method for diesel engine combustion in an internal combustion engine having one or more cylinders is proposed, each having a displacement of at most 250 cm ³ . Each cylinder is associated with a single inlet and a single outlet valve, which are preferably operated for gas exchange using a variable valve lift and for generating a variable swirl in a swirl-shape along a circumferential piston recess in a piston head into which a conically spanned fuel injection from an at least approximately centrally arranged in a cylinder head injection device takes place. Preferably, the method is carried out with the diesel internal combustion engine described above. By way of example, the method provides for a swirl, preferably a swirl vortex, to be guided along the piston recess and to rotate during a piston movement in the direction of a top dead center along a conical boundary of the combustion chamber formed by the cylinder head. A further embodiment provides that at least approximately in an upper dead position of the piston, an injection jet enters the piston recess and impinges on the bottom thereof, wherein the bottom in cross-sectional view, for example, the shape of a Muldenellipse along which the injection jet by a rotating swirl vortex is homogenized to a fuel-air mixture. Furthermore, it can be provided that the swirl vortex rotates about a dome extending from the piston head in the direction of the cylinder head cover, wherein the dome causes a displacement in a region around the injection in the direction of the piston crown when approaching the cylinder head cover. In this case, the calotte extending from the piston crown preferably interacts with the conical shape which forms the upper boundary in the cylinder head for the combustion chamber. Furthermore, the method can use one or more embodiments of the proposed internal combustion engine, wherein the respective advantages can be combined with each other.

Further advantageous embodiments are explained in more detail in the following figures. However, the resulting from the individual figures features are not limited to the individual embodiments. Rather, these can be one or more Characteristics of other figures as well as from the above description are linked to further developments. Moreover, the features resulting from the individual figures are not intended to be restrictive, but serve to illustrate the invention by way of example. Show it:

1 is a first schematic view of a possible embodiment of a cylinder of the proposed diesel internal combustion engine,

2 shows a second illustration of the cylinder of FIG. 1 with exemplary swirl flow, FIG.

Fig. 3 in top view a boundary view with respect to an achievable

CO ₂ levels as a function of various desired downsizing degrees for internal combustion engines in passenger cars, and in the lower diagram a consideration of the required specific ones

Performances of the engines considered in the above figure, both figures being related to different weight classes and the engines having an assumed mean power rating being considered here,

4 shows in the upper illustration a dependency of a peak cylinder pressure on the specific power for a given configuration of a compression ratio of 15: 1 and a specific, related to the displacement hydraulic flow, wherein in the figure below for the different motors of FIG Figure 3 shows a peak pressure requirement versus weight.

Fig. 5 shows a further possible embodiment of a piston crown geometry, shown as a schematic view of a half.

Fig. 1 shows a schematic view of a section of a diesel internal combustion engine 1. Shown is a cylinder 2, which has a displacement of up to 250 m ³ . The displacement is to be understood as the displacement which lies in the cylinder between top dead center OT and bottom dead center UT. A combustion chamber 3 is bounded at the top by the cylinder head 4, down through a piston 5. The cylinder head 4 has a boundary 6 for the combustion chamber 3 as a conical shape. The conical shape is preferably completely rotationally symmetrical and thus forms in cross sections perpendicular to a cylinder axis 7 at least approximately circular cross-sectional areas. The piston 5 has a piston recess 8. For this purpose, the piston 5 preferably has, for example, a flat edge surface 9 with a width B. This is preferably between 2 and 5 mm, preferably 3 mm. From the edge surface 9, the surface of the piston 5 lowers, thereby forming the piston recess 8. A depression as well as a subsequent increase in the piston recess may for example have a radius R1, which is preferably between 40 and 46 mm. The radius R1 can transition to a second radius R2. The second radius describes the shape of a hill 10. This can be dome-shaped. Around the elevation 10, the piston recess 8 preferably extends in the circumferential direction in a symmetrical cross-sectional configuration. In this way, in addition to the boundary 6 and the piston 5 constructed rotationally symmetrical, both preferably have the same axis of rotation, namely the cylinder axis 7. It is further preferred that an injection 11 is provided by means of an injection device, which likewise extends along the cylinder axis 7. An injection valve of the injection 11 has injection jets 12 which form a cone angle β of the injection jets 12. The injection jets 12 are preferably aligned so that they can impinge on the bottom of the piston recess 8. In particular, the cone angle β of the injection jets 12 is designed so that a lower Muldenellipse the piston recess 8 is made centrally in the top dead center. Preferably, a cone angle β of about 80 ° is provided for this purpose. This results in a very good homogenization in the combustion chamber 3, especially at an early start of injection. Furthermore, an inlet valve 13 and an outlet valve 14 are provided. The intake valve 13 has an inclination angle α E with respect to the cylinder axis 7, the exhaust valve 14 has an inclination angle α A relative to the cylinder axis 7. Preferably, both inclination angles α E and α A are the same. They are preferably about 24.5 °. The inclination angle can also be different. For example, the inclination angle α E may be greater than the inclination angle α A, or vice versa. A valve seat diameter D in turn of inlet or outlet valve is preferably 34 mm. The cylinder 2 may further have a variable valve drive 17, which is indicated only schematically. The variable valve train is actuated, for example via an engine control 18, whereby the timing of intake and / or exhaust valve 13, 14 can be adapted to different situations.

2 shows an inflow 19 of combustion air, which may be charged by means of a compressor 20, for example. The compressor can be driven, for example mechanically, electrically or in any other way. A charge of burning ventilation can also be effected by other means. The inlet valve 13 preferably has a phase 21 on the associated valve seat. If, for example, the inlet valve 13 is not raised completely, but only slightly, a swirl inflow can be achieved via this phase 21, which adjusts itself rotatingly about the cylinder axis 7. In this way, with appropriate injection, a particular homogenization of the fuel-air mixture to be burned done, since the free jets from the injection 11 with their free jet lengths along a circumference of the injection cone viewed at least approximately identical.

The principle of downsizing proposed in this diesel internal combustion engine 1 thus makes use, on the one hand, of a special symmetry formation of a flow and, on the other hand, of a jet length which is directed in particular to the trough. To achieve a compression, the elevation 10 is provided next to the trough, so that in this way a displacement of between 100 and 250 m ³ can preferably be set for the proposed diesel internal combustion engine. Preferably, over a cross-sectional area of the piston 5 along the edge surface 9 perpendicular to the cylinder axis 7 about at least 55% to about 75%, preferably at least about 80% of the surface formed as a piston recess 8 projected on this cross-sectional area, while the surface of the hill 10 projected on the cross-sectional area is preferably between 5 to 35%. The injection jets, which in this case form a cone angle, can in this case be produced by means of a hole nozzle which generates a corresponding cone. The formation of a swirl vortex as shown, for example, is supported by an eccentric seat. Here, a swirl-induced flow can be adjusted for small valve strokes, by means of the choice of the inclination of the respective valve, a filling of the combustion chamber on the one hand and on the other via the seat design generating a swirl and total thus a directed homogeneous flow as shown.

FIG. 3 and FIG. 4 show a relationship by means of which a downsizing for use in the vehicle sector for the proposed diesel internal combustion engine proves to be advantageous and also executable. This is shown by means of different displacement sizes, which are exemplified as 3I, 2,2I-1, 61, 1, 21 and 0.81-displacement engines.

Against the background of the discussion on the reduction of CO ₂ emissions, various concepts for improving the use of energy in individualized passenger transport are discussed. A very promising measure is downsizing. This is also propagated for diesel engines, so that, for example, by over- From a 2.0 to 1.6-liter engine with additional combustion improvement CO ₂ reduction potential of up to 17% can be achieved. However, these are conventional process concepts with Einzelhubvolumina of about 400 cc.

In the following, a first limit value analysis with regard to the achievable CO ₂ level is carried out as a function of the desired degree of downsiging, as becomes clearer from FIGS. 3 and 4.

On the basis of a modern EUV diesel engine, the CO ₂ values in the NEDC were calculated for a constant characteristic cw ^* A (drag coefficient x vehicle front surface) of 0.7 as a function of the flywheel mass class. The engines are based on a 3.0-liter 6-cylinder, 2.2-liter 4-cylinder, 1, 6-liter 4-cylinder, 1, 2-liter 3-cylinder and 0.8-liter 2-cylinder.

The trend shows that even with a 1, 6-liter engine in the configuration considered here, the CO ₂ target values can be met according to the NEDC specification, while the 2.2 and 3-liter engines are above it. By further reducing the stroke volume to 0.8 and 1.2 liters, the consumption can be further reduced, the advantages becoming smaller, since the improvement in the ratio of the friction medium pressure to the effective medium pressure decreases as the downsizing degree increases. With an additional mass balance beyond the friction of the engine is greater.

To illustrate the required specific performances of different degrees of downsizing, the required specific performances of the engines considered here for an assumed mean nominal power of different weight classes are shown in FIG. 3 at the bottom left. A 0.8-liter engine comes with this specification already from 1000 kg to 75 kW / L, a 1.2-liter engine from 1.300 kg, while both a 1.6-liter and 2.2-liter Motor in the entire range below 82 kW / L are.

The depictability of high specific power is linked to the thermal and mechanical load capacity of the engine. The latter is shown in Fig. 4, top right. For a given configuration of the compression ratio of 15: 1 and a specific, related to the displacement hydraulic flow rate of 1, 55 cm ³ / 60s @ 100 bar / cm ^3, the dependence of peak cylinder pressure, shown here on the specific results see performance. With the measures listed in FIG. 3 and FIG. 4, 80 kW / L can be represented with a combustion peak pressure of 190 bar. This information can be linked to the specific performance required resulting peak pressure for the different engines, the peak pressure requirements are shown as a function of the weight, cf. Fig. 4 bottom right. Accordingly, the 0.8-liter engine reaches a required peak pressure of more than 180 bar from as little as 1000 kg. A 1, 2-liter engine could be used up to 1400 kg and a required peak pressure of 200 bar.

The 1, 6 and 2.2 liter engines are to be used throughout the range considered when the 1.6-liter engine is jerk-proof up to 200 bar.

Designing for lower specific power results in shifting these curves to the right and may result in a wider range of applications for the small engines considered here.

With a more optimized CO ₂ concept and correspondingly reduced power, the range of application of the 0.8-liter engine can be increased. However, concepts are also possible in which a 1-liter engine is represented as a 4-cylinder engine and thus with a 250 cc single-stroke volume or less. These motors can be designed without balance shaft and also offer advantages in terms of charge exchange.

FIG. 5 shows a further possible embodiment of a piston crown which, according to a development, extends at least approximately rotationally symmetrically about a cylinder axis. The piston crown has a circumferential depression whose center of gravity is displaced in the direction of the piston edge: a lowest point of the depression is arranged closer to the piston edge than to the center of the piston. Furthermore, a bowl wall close to the piston rim drops much steeper than a bowl wall arranged nearer to the center of the piston, which extends in a tilting manner from an elevation arranged in the center of the piston in the direction of the piston edge. The trough wall close to the edge preferably falls off at least approximately vertically, and according to one embodiment may even form an indentation here. Preferably, the piston crown is rounded over to a lowest point of the trough bottom, from where the trough bottom rises again in the direction of the hill. According to a development, the piston crown can interact with an injection in such a way that different beam deflections can be made possible. Different possibilities are represented schematically by different courses. In this case, an injection jet can be redirected as a gaseous form or as a still liquid fuel, for example in the form of drops. According to one embodiment, an injection jet itself can have a circumferential component pointing in the circumferential direction without a lateral directional component and according to another embodiment. In this case, this For example, counteracting a twist direction or act in the direction of a twist effect, which is indexed by an inlet flow in the combustion chamber. Thus, for example, the injection may be such that the injection jet first contacts the hollow bottom and is deflected by the latter, before the fuel then also changes its circumferential direction component due to the deflection. In this way, for example, an improved homogenization can take place.

In addition to use as the sole drive preferably a small vehicle or a hand tool, a supplementary or alternative drive use may be borrowed lent. In addition, more and more "plug-in hybrid" concepts are currently being discussed with small internal combustion engines as range extenders. Also in this context, the proposed diesel internal combustion engine, for example, as a small and inexpensive diesel engine with, for example, more than 2 cylinders and Einzelhubvolumina between 200 and 250 cem can be used as an efficient range extender. These motors can be consistently designed for use in a narrow speed and load range and optimized in terms of fuel consumption and emissions.

In a further embodiment, motorcycles or other light vehicles, especially in emerging countries with diesel engines are used, since they allow high efficiency.

As well as being used in a vehicle, the principle of the diesel internal combustion engine can also be used, as proposed, for example in a generator which is driven by means of the proposed diesel internal combustion engine. For this example, a single cylinder is used. However, it can also be multi-cylinder solutions. Furthermore, the principle can also find application in hybrid engines. It is also possible to use implements, in particular, for example, chainsaws, hand tools or other with the proposed diesel internal combustion engine.

Claims

claims

A diesel internal combustion engine having at least one or more cylinders (2), each having a displacement of approximately at most 250 cc, preferably less than 250 cc, wherein a cylinder (2) has a boundary of a combustion chamber (3) in the form of cones by a cylinder head (4) of the diesel internal combustion engine (1) has an injection (11) which is arranged at least approximately centrally and centrally in the conical shape, a piston (5) with a piston recess (8), an inlet valve and channel arrangement and geometry for generating a swirl in the combustion chamber (3) of the cylinder (2), and each provided with a single inlet and outlet valve (13, 14), wherein the inlet and the outlet valve (13, 14 ) are arranged opposite one another in the cylinder head (4).

2. Diesel internal combustion engine (1) according to claim 1, characterized in that the inlet and the outlet valve (13, 14) in the closed state flush with a surface of the cylinder head (4).

3. Diesel internal combustion engine (1) according to claim 1 or 2, characterized in that a variable valve train (17) for changing a valve lift over the speed range of the diesel internal combustion engine (1) is provided.

4. Diesel internal combustion engine (1) according to claim 1, 2 or 3, characterized in that the piston (5) with the piston recess (8) forms a rotationally symmetrical limitation of the displacement (3).

5. Diesel internal combustion engine (1) according to any one of the preceding claims, characterized in that the piston recess (8) has a round, in particular annular channel shape.

6. Diesel internal combustion engine (1) according to any one of the preceding claims, characterized in that the piston recess (8) is axisymmetric.

7. Diesel internal combustion engine (1) according to any one of the preceding claims, characterized in that the piston recess (8) falls radially inwardly from an outer edge of the piston and rises again to the center of the piston.

8. Diesel internal combustion engine (1) according to claim 7, characterized in that the piston recess (8) in the region of the piston center has a rise (10) which rises above the piston edge in the direction of the cylinder head (4).

9. Diesel internal combustion engine (1) according to any one of the preceding claims, characterized in that the piston recess (8) has a lowest point, which is arranged closer to a piston edge than to a piston center.

10. Diesel internal combustion engine (1) according to any one of the preceding claims, characterized in that injection jets of the injection (11) have a cone angle ß, which is between 70 ° and 90 °, relative to an axis through an injection nozzle of the injection.

11. Diesel internal combustion engine (1) according to one of the preceding claims, characterized in that the inlet and the outlet valve (13, 14) each have an inclination angle α between a valve axis and a cylinder center axis, which is in a range between 20 ° and 30 ° lie.

12. Diesel internal combustion engine (1) according to claim 11, characterized in that the inlet and the outlet valve (13, 14) have the same inclination angle α sen.

13. Diesel internal combustion engine (1) according to any one of the preceding claims, characterized in that in the cylinder head (4) for the inlet and the outlet valve (13, 14) each have a valve seat diameter D is provided, which is between 20 mm to 37 mm ,

14. Diesel internal combustion engine (1) according to claim 13, characterized in that the valve seat diameter D of the inlet and the outlet valve (13, 14) is at least approximately equal.

15. A method for diesel engine combustion in an internal combustion engine with one or more cylinders (2), each having a displacement of at most 250 cc, wherein a single inlet and a single exhaust valve (13, 14) per cylinder (2) and present for Gas change preferably using a variable valve lift are actuated to produce a variable swirl swirl along a circular piston recess (8) in a piston head into which a conically spanned fuel injection from an at least approximately centrally in a cylinder head (4) arranged injection (11) takes place.

16. The method according to claim 15, characterized in that a swirl vortex guided along the piston recess (8) and during a piston movement in the direction of a top dead center (TDC) along a through the cylinder head (4) formed conical boundary (6) of the combustion chamber (3) flows in a rotating manner.

17. The method according to claim 15 or 16, characterized in that at least approximately in an upper dead position (TDC) of the piston (5) an injection jet enters the piston recess (8) and thereby impinges on the bottom thereof, wherein the bottom in cross-sectional view the shape has a trough ellipse along which the injection jet is homogenized by a rotating swirl vortex into a fuel-air mixture.

18. The method according to any one of the preceding claims, characterized in that a swirling vortex about a piston bottom in the direction of boundary (6) of the cylinder head (4) rotates dome, wherein the dome when approaching the cylinder head cover a displacement of a gas mixture in causes an area around the injection (11) in the direction of the piston crown.

19. Application of a diesel internal combustion engine (1) according to one of the preceding claims as a motorcycle drive.

20. Application of a diesel internal combustion engine (1) according to one of the preceding claims as a vehicle drive, in particular as a motor vehicle drive.

21. Application according to claim 20 as a range extender.

22. Application of a diesel internal combustion engine (1) according to one of the preceding claims as a generator.

23. Application of a diesel internal combustion engine (1) according to one of the preceding claims with a number of cylinders between one to six.